Carboxyl content

The method of choice for determining carboxyl groups in lignin is based on potentiometric titration in the presence of an internal standard, /)-hydroxybenzoic acid, using tetra- -butylammonium hydroxide as a titrant (42). The carboxyl contents of different lignins are shown in Table 6. In general, the carboxyl content of lignin increases upon oxidation. 

There have been other approaches to obtaining rubber/metal adhesion besides primers or additives consisting of phenolics or epoxies plus halogenated elastomers. For example, carboxylated polymers (olefins and diolefins copolymerized with acrylic acid monomers) have shown excellent adhesion to metals. Very little carboxyl is necessary, and polymers with carboxyl contents as low as 0.1% show good adhesion when laminated to bare steel. When these materials possess... 

In Table 4, intrinsic viscosities and carboxyl contents of different fractions of modified PS obtained at different catalyst media are presented. As evidenced from these data, all PS samples used were acylated. As the viscosity of the fractions decreases, the carboxyl contents in the product increase. The highest degree of acylation for all fractions is observed when BF3-OEt2 is used as the catalyst. 

As a result of oxidation, the adhesion strength between PE and A1 is found to increase by about 8 to 28 times. The adhesion strength increases with an increase in carboxyl content, total amount of oxo- groups, and the combined carboxyl and carbonyl content. 

Highly concentrated ether carboxylic acids with a low degree of ethoxylation even at room temperature can give an esterification reaction with the non-converted nonionic, especially with the fatty alcohol, to several percentage points. The result may be that a too low value is found for the ether carboxylate content. This mistake in analysis can be avoided by saponification of the formed ester [238]. Two hundred to 300 mg matter and ca 100 mg NaOH were weighed in a 50-ml Erlenmeyer glass, heated with 20 ml ethanol under reflux, and after cooling supplied with water to 100 ml. Afterward a two-phase titration was carried out. 

Hydrolysis of amide groups to carboxylate is a major cause of instability in acrylamide-based polymers, especially at alkaline pH and high temperatures. The performance of oil-recovery polymers may be adversely affected by excessive hydrolysis, which can promote precipitation from sea water solution. This work has studied the effects of the sodium salts of acrylic acid and AMPS, 2-acrylamido-2-methylpropanesulfonic acid, as comonomers, on the rate of hydrolysis of polyacrylamides in alkaline solution at high temperatures. Copolymers were prepared containing from 0-53 mole % of the anionic comonomers, and hydrolyzed in aqueous solution at pH 8.5 at 90°C, 108°C and 120°C. The extent of hydrolysis was measured by a conductometric method, analyzing for the total carboxylate content. 

The extent of hydrolysis of the copolymers was determined by conductometric titration. The increase in carboxylate content was determined by difference, before and after hydrolysis. (The AMPS content of the polymers, where measured, was determined by colloid titration with poly [diallyl dimethyl ammonium chloride].)... 

The rate of hydrolysis of acrylamide in copolymers with sodium acrylate or AMPS, 2-acrylamido-2-methylpropanesulfonic acid, decreased as the proportion of the anionic comonomers was increased. This effect was much more marked with AMPS than with sodium acrylate, and occurred at 90°, 108°, and 120°C. Typical results at 108°C [Figs. 1 and 2] show the increase in carboxylate content of acrylamide copolymers containing sodium acrylate and AMPS respectively. 

The total carboxylate content in a range of sodium acrylate copolymers is shown in Fig. 4, calculated as the sum of the initial carboxylate and carboxylate formed during hydrolysis. These values may be compared with the total carboxylate content in AMPS copolymers [Fig. 2]. 

The c-spectrum shows more carboxylic content (ketonic absorbance at 1716 cm l), meaning that the prestrain has enhanced the photodegradation of the polymer. 

Duh, B., Method for production of a high molecular weight polyester prepared from a prepolymer polyester having an optimal carboxyl content, US Patent 4 238 593, 1980. 

Bikiaris and Karayannidis [5] have investigated the use of diimidodiepoxides as chain extenders for PET resins. Starting with a PET having an IV of 0.60 dL/g and a carboxyl content (CC) of 42 eq/106 g, they obtained PET with an IV of 1.16 dL/g and a CC below 5 eq/106 g. The typical reaction condition for the coupling of PET was heating with the chain extender under an argon atmosphere above its melting temperature (280 °C) for several minutes. 

Rivin 83,84) found a close agreement between NaHCOj neutralization by carbon blacks and their adsorption capacity for diphenylguanidine from benzene solution. The carbonate neutralization, again, was twice the bicarbonate value 84). The carbon dioxide evolved on vacuum pyrolysis was roughly equivalent to the carboxyl content. 

According to Scheme 12, the alkaline peeling of cellulose should continue until the entire polymer is degraded. However, cellulose dissolves partially, but not completely, in hot alkali, and this remaining polysaccharide contains an increased carboxyl content.Thus, a second reaction is occurring that competes with the step-wise, peeling procedure. 

We seek to determine an effective fixed-charge density which influences ion uptake and transport. This may be different from an analytical determination of total carboxyl content because some groups may not be in swollen regions of the polymer and so may not... 

Viscosity measurements on a series of CPSs having the same polymerization degree but different carboxyl contents have provided clear evidence for self-association in solutions. Figure 30 shows the reduced viscosities in butanone and THF (2 mg/ml) at 30.0 °C as a function of carboxyl content. When the carboxyl content is below 3.4 mol%, the reduced viscosity decreases as carboxyl groups are introduced into the CPS. This behavior reflects the constriction of polymer... 

Surprisingly, the G3 fraction (Figure 11) shows almost the complete opposite behavior. The phenol peak becomes predominant, and this change is expressed in Figure 12, where the relative surface areas (response) of three typical fragments (base peaks for pyrrole, phenol, and 2-cyclopenten-l-one) are shown for line I. Similar results were obtained for line II (ozonation 5 mg/L for 10 min) where a high carboxylic content was also found (Figure 13). 

In oxidized cellulose, part of the terminal primary alcohol groups of the glucose residues are converted to carboxyl groups. The product should contain no less than 16% and no more than 24% carboxyl groups. Products with low carboxyl content have better technical properties. Oxidized cellulose is a fibrous white powder prepared from cotton wool and posesses a slight acid odor. 

The compositions of stearic and behenic acid films over substrates containing 0.1M sodium ions in the pH range 4 to 9.7 have been determined (3) by skimming the fatty acid film off the surface and determining carboxylate content by infrared analysis. The evidence of the present study, however, suggests that even at bulk pH 9.7, stearic and behenic acid films are not completely saponified. 

Table II. Carboxyl Content of Kerogen and Trona Adds...

C = carbon content (%) of solid reactant OH = hydrogen content (%) of solid reactant > TA = total addity in meq./gram Q COOH = carboxyl content in mea./gram HA = "humic add —i.e., alkali soluble material in w/w % of reactant... 

As the viscosity of the reaction system increases, it becomes more difficult for ethylene glycol to diffuse through the reaction system and be eliminated from it. Thermal decomposition also occurs under melt polycondensation conditions, resulting in an increase of terminal carboxyl content and a decrease of hydroxyl ends that lower the apparent polycondensation rate even further. 

Analytical Procedure. The intrinsic viscosity [t Jocp was calculated from the value measured in o-chlorophenol at 35°C. Reduced viscosity rjBP/c was measured by a viscometer at 35°C after dissolving 120 mg of sample in 10 ml of o-chlorophenol at 100° C. The carboxyl content was... 

Hydrolytic Stability. Hydrolytic stability of PET filaments obtained by the chain extender method was examined by holding the filaments at 150° C for six hours at 100 relative humidity. The results shown in Figure 11 indicate that the hydrolytic stability of PET decreases with increasing carboxyl content. 

---